East and west and south and north

Oldweather is now really hitting its stride, with a stream of ships reaching completion and so becoming available for analysis. One of those that has completed recently is the battlecruiser HMS New Zealand, which was named for the country that funded her construction, and carried Admiral of the Fleet John Jellicoe on a tour to India, Australia, New Zealand and Canada in 1919. Her logs from this circumnavigation are those we’re looking at in Oldweather.

Long voyages like this are particularly desirable as a source of weather observations, because the same ship, crew and weather instruments experience and record a wide range of different weather conditions; from the hot calms of the doldrums, through the steady trade-wind regions, to the stormy conditions of the roaring forties. On her circumnavigation New Zealand sees all of these conditions, and the change in weather conditions shows up clearly in her barometer records – Captain toucans, Lieutenants keybasher, jdulak, Cyzaki, and all her crew have provided a good picture of the weather in 1919, over a wide section of the world.

So the records digitised from the New Zealand, like those from the other ships completed so far, have been entered with accuracy and skill; but there is always one component of the data that presents us with more trouble than the others, and for the Oldweather ships, it’s the ship positions. Many of you will have noticed that the maps showing the ship positions as they are being entered sometimes show unlikely or impossible positions – HMS New Zealand’s positions are not unusually problematic, but, because the ship travelled so widely, they make a good example to illustrate the issue. The figure below shows the positions digitised for the New Zealand.

Raw position records for HMS New Zealand: Blue points mark the most popular entries for each log-page, red points mark other entries.

It’s clear where the ship was going, and it’s also clear that sometimes we’re getting the positions wrong. In this case, all the wrong positions have the same cause – we know the longitude, but not whether it’s East or West of Greenwich.

Position of HMS New Zealand on May 7th 1919

This image shows a typical at-sea position entry – we can see that the latitude is 2 degrees 17 minutes, and the longitude is 88 degrees 5 minutes, but the letters showing the position as south of the equator (`S’) and east of Greenwich (`E’) are a bit detached from the position entries. The position of these letters seems to vary from log to log – sometimes they are put immediately after the position values, sometimes merely nearby, as here. But either way, please always enter them along with the positions, so this example should be entered as latitude “2 17 S” and longitude “88 5 E”.

Even if we always enter the direction letters, we won’t get rid of all position errors of course – sometimes the letters are missing in the log, sometimes the log-keeper makes a mistake entering the position. It’s important to faithfully reflect the logs, so we shouldn’t try to fix such problems. But please do enter them however they appear on the page.

Boxing the compass is harder than it seems at first. ‘NW’ and ‘N by W’ are both valid wind directions, and they are not the same. You can never go wrong by entering exactly what it says in the log, Directions can be pretty obscure: ‘NE by E 3/4 E’ is a valid direction, for example.